Prusa firmware for RAMPS Prusa i3 clones with MK42 beds

3D Modelling, Slicing, Hosts and Management
IanC
Posts: 20
Joined: Sat Aug 12, 2017 11:55 pm

Re: Prusa firmware for RAMPS Prusa i3 clones with MK42 beds

Post by IanC » Tue Aug 29, 2017 8:24 pm

Thanks :). I think I'll connect the Z steppers in series, but it's good to know I can just use E1.

I had a look at the Prusa source code to get an idea for the current to use with my steppers, and I found this line:

#define DEFAULT_PWM_MOTOR_CURRENT_LOUD {540, 830, 500} // {XY,Z,E}

If those values are in mA then they seem rather small? It means that the A4988 Vref is only around 0.4V. Did you base your config on similar values? I followed the Pololu driver wiki you posted earlier on, but my steppers can handle up to 2.5A which is a so much higher than it appears Prusa drive theirs at.

IanC
Posts: 20
Joined: Sat Aug 12, 2017 11:55 pm

Re: Prusa firmware for RAMPS Prusa i3 clones with MK42 beds

Post by IanC » Tue Sep 05, 2017 3:47 pm

The last parts arrived today and the printer is now up and running :). It's half way through the first print at the moment. The x-carriage is extremely noisy, so I've got a bit of troubleshooting to do - but it works :D .

Thank you for porting this firmware over!

slippyr4
Posts: 224
Joined: Thu Jun 15, 2017 10:24 am

Re: Prusa firmware for RAMPS Prusa i3 clones with MK42 beds

Post by slippyr4 » Tue Sep 05, 2017 3:58 pm

Sorry, i meant to reply to your previous post but never got round to it. Presumably therefore, you figured out the problem? what was it?

RAMPS and the MKS boards don't have any digipot type hardware for setting stepper currents in firmware.This means that the Quiet Mode / High Power settings in the firmware have no effect It would be possible to add external pots or other electronics, and then modify the stepper drivers to take that input, but for me at least I can't see the point.

Admittedly I don't have a genuine prusa with a genuine RAMBo, but, I can't see that i'd ever want to risk print defects or failed prints by running in "quiet mode" (which is merely reduced stepper current).
Self-built Prusa i3 MK2 clone
My things: https://www.thingiverse.com/slippyr4/designs
My Prusa firmware port for ramps & MKS : https://github.com/slippyr4/Prusa-Firmware

slippyr4
Posts: 224
Joined: Thu Jun 15, 2017 10:24 am

Re: Prusa firmware for RAMPS Prusa i3 clones with MK42 beds

Post by slippyr4 » Tue Sep 05, 2017 3:58 pm

IanC wrote:
Tue Sep 05, 2017 3:47 pm
It's half way through the first print at the moment.
Photos then please!
Self-built Prusa i3 MK2 clone
My things: https://www.thingiverse.com/slippyr4/designs
My Prusa firmware port for ramps & MKS : https://github.com/slippyr4/Prusa-Firmware

TheBat
Posts: 13
Joined: Thu Jun 15, 2017 12:18 am

Re: Prusa firmware for RAMPS Prusa i3 clones with MK42 beds

Post by TheBat » Tue Sep 05, 2017 4:44 pm

slippyr4 wrote:
Sun Jul 23, 2017 12:14 pm
No multimaterial support at the moment. I will look into that in the future, but so far the electronics for the extruder multiplexer board isn't publically available and that makes it more trouble than it's worth to try and implement that on a clone.
A bit off topic, but by reading the ids on the chips on pictures of the board and looking at the FW change, the new PCB should just be a 3-bit multiplexer and some 2-channel relays.

IanC
Posts: 20
Joined: Sat Aug 12, 2017 11:55 pm

Re: Prusa firmware for RAMPS Prusa i3 clones with MK42 beds

Post by IanC » Tue Sep 05, 2017 4:52 pm

slippyr4 wrote:
Tue Sep 05, 2017 3:58 pm
Sorry, i meant to reply to your previous post but never got round to it. Presumably therefore, you figured out the problem? what was it?

RAMPS and the MKS boards don't have any digipot type hardware for setting stepper currents in firmware.This means that the Quiet Mode / High Power settings in the firmware have no effect It would be possible to add external pots or other electronics, and then modify the stepper drivers to take that input, but for me at least I can't see the point.

Admittedly I don't have a genuine prusa with a genuine RAMBo, but, I can't see that i'd ever want to risk print defects or failed prints by running in "quiet mode" (which is merely reduced stepper current).
No problem :). I'm very grateful for all the help. I just set them to those approx mA values using the trim pots, but there's some tuning to be done, as you may see from the photos ;):

http://imgur.com/a/tP6Km

There is a huge rattle when the extruder moves along the x axis, I'm not sure what is causing that - but when it's powered off it slides as smooth as butter. I guess it's the stepper causing this, but I don't know why - I tried tweaking the voltage +/- 50% to no avail, so it doesn't seem related to stepper power. There are also some missed layers for some reason.

Lots to work on, but considering it's only just assembled, I'm pleased! :)

slippyr4
Posts: 224
Joined: Thu Jun 15, 2017 10:24 am

Re: Prusa firmware for RAMPS Prusa i3 clones with MK42 beds

Post by slippyr4 » Tue Sep 05, 2017 4:56 pm

TheBat wrote:
Tue Sep 05, 2017 4:44 pm

A bit off topic, but by reading the ids on the chips on pictures of the board and looking at the FW change, the new PCB should just be a 3-bit multiplexer and some 2-channel relays.
i've not studied at all. there's two versiobs of the electronics - the older is all solid state but the only pics i've seen i can't see the part numbers. the newer version has 3 dual SPDT relays on it, which isn't really enough to switch 4 motors into 1, so not sure what else is on that board either.
Self-built Prusa i3 MK2 clone
My things: https://www.thingiverse.com/slippyr4/designs
My Prusa firmware port for ramps & MKS : https://github.com/slippyr4/Prusa-Firmware

IanC
Posts: 20
Joined: Sat Aug 12, 2017 11:55 pm

Re: Prusa firmware for RAMPS Prusa i3 clones with MK42 beds

Post by IanC » Tue Sep 05, 2017 5:35 pm

I've just changed the X driver from A4988 to DRV8825 and it made a world of difference to the extruder carriage noise - I've got some TMC2100's on the way to see how they perform. :).

redan
Posts: 1
Joined: Sun Sep 17, 2017 12:51 pm

Re: Prusa firmware for RAMPS Prusa i3 clones with MK42 beds

Post by redan » Sun Sep 17, 2017 12:54 pm

Works like a charm, thanks.

Small question. how do you guys power the lcd screen. It seems to only get power when usb is connected. Have search around for a way to power it with out usb but can not find an easy solution.

IanC
Posts: 20
Joined: Sat Aug 12, 2017 11:55 pm

Re: Prusa firmware for RAMPS Prusa i3 clones with MK42 beds

Post by IanC » Mon Sep 25, 2017 3:22 pm

IanC wrote:
Tue Sep 05, 2017 5:35 pm
I've just changed the X driver from A4988 to DRV8825 and it made a world of difference to the extruder carriage noise - I've got some TMC2100's on the way to see how they perform. :).
Just a quick update. I'm now running with TMC2100's and they're near silent :).

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